A near-vertical rear roof slope with flat top — maximum space and a premium finish, popular on Victorian terraces. Compare up to 3 free quotes — no obligation.
A mansard conversion replaces the rear roof slope with a near-vertical wall (typically at 72 degrees) topped with a flat roof, creating a room that is almost box-shaped throughout its entire area. Mansard conversions offer the maximum amount of space of any conversion type and are the premium choice for adding a large, full-height loft room.
Mansard conversions almost always require planning permission as they significantly alter the appearance of the property, particularly on terraces where a whole run of mansards can be done simultaneously. Your specialist will manage the planning process as part of the project.
Typical cost: rear mansard conversion £40,000–£65,000. Mansard with en-suite or high specification £55,000–£80,000+.
Prices vary by region, subfloor condition and product choice. Compare 3 quotes for the most accurate price for your specific job.
“We had a rear dormer conversion done last summer — extra bedroom and en-suite for our teenage daughter. Got three quotes through this site, saved around £4,000 compared to the first firm we spoke to. The specialist handled planning permission and building regs start to finish. Highly recommend.”
“Hip-to-gable conversion on our 1930s semi. I was nervous about the planning application but the specialist I found here had done dozens in our street and knew exactly what to submit. Project came in on time at 10 weeks. The new master bedroom is brilliant.”
“L-shaped dormer on our Victorian terrace — created two rooms and a bathroom from what was a completely unusable loft. The comparison process gave me confidence I was paying a fair price. Building control sign-off came through with no issues. Absolutely transformed the house.”